Older (manual focus, legacy) zoom lenses usually aren't very good by today's standards, and so-called "macro" zooms are not corrected for close-up use the way true macro primes are. (The exceptions are expensive, discontinued true macro zooms like the 70-180mm Micro-Nikkor and the 90-180mm Vivitar Series 1 Flat Field Zoom). If you're serious about macro of bugs, you should get a true macro of at least 90mm. You could get a Minolta MC 100mm macro for $100 or even less. A Canon FD would be similar in price & quality.